Browse Prior Art Database

Unauthorized Copy Prevention

IP.com Disclosure Number: IPCOM000080140D
Original Publication Date: 1973-May-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Boggs, BR: AUTHOR [+2]

Abstract

Information that is not to be copied is printed on conductive paper 10. Copy machines 11 located in the area where security documents are stored are provided with detecting circuitry, comprising an oscillator circuit 12 that includes a coil 13 located adjacent the document exposure window 14, and a variable capacitor 15 for fine adjustment. The output frequency of oscillator 12 is a function of the inductance of coil 13, and is compared by circuit 16 with a reference frequency generated by a second oscillator 17. If the frequencies supplied by oscillators 12 and 17 are not identical, frequency compare circuit 16 emits a control signal on line 18 to disable the copy machine 11 and sound alarm 19.

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Unauthorized Copy Prevention

Information that is not to be copied is printed on conductive paper 10. Copy machines 11 located in the area where security documents are stored are provided with detecting circuitry, comprising an oscillator circuit 12 that includes a coil 13 located adjacent the document exposure window 14, and a variable capacitor 15 for fine adjustment. The output frequency of oscillator 12 is a function of the inductance of coil 13, and is compared by circuit 16 with a reference frequency generated by a second oscillator 17. If the frequencies supplied by oscillators 12 and 17 are not identical, frequency compare circuit 16 emits a control signal on line 18 to disable the copy machine 11 and sound alarm
19.

The inductance of coil 13 is significantly changed by the presence of conductive paper 10 on exposure window 14. Thus, an attempt to copy a security document changes the output frequency of oscillator 12, to disturb the normal balanced condition of frequency compare circuit 16 and disable the copy machine 11.

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